1906.] OF THE TRACHEOPHOXE PASSERES. 155 



the forms now under discussion. These trochlete are not only 

 all in the same plane, but they are also all of the same length ; in 

 their relative sizes, however, they show not inconsiderable 

 diffei^eiaces. 



The Oonopophagina? show the least specialised condition of 

 these parts, in that all trochlese are large and placed wide apart. 

 The II. is turned inwards. In the PteroptochiiiJe all are small : 

 and they are still further, relatively, reduced in the Pipridaj, 

 especially in so far as IV. is concerned. In the Pipridee III. is the 

 largest, IV. the sixiallest. 



Among the Formicariine and Dendrocolaptine types there 

 appears to be a marked tendency to reduce the IV., and this is well 

 seen in Homorus, whei-e trochlese II. and III. are large, and IV. 

 extremely sanall. The same is true of Pseudocolaptes and Batara, 

 thoiigh not to so marked an extent. In Dendrocolaptes the 

 trochle^e are wide apart, and III. is deeply cleft in the middle. 

 Xiphorhynchus is peculiar in having a rather small II. trochlea 

 which is turned inwards, while III. is deeply cleft as in Dendro- 

 colaptes. 



The depression for Mc. I. is generally well marked, especially 

 so in Homortos. 



The Formicariine, Dendrocolaptine, and Synallaxine types agree 

 with the Conopophagida3 in that Ph: I. of D. IV. is only about half 

 the length of the same phalanx in D. II. III. In Fseudocolaptes 

 all the phalanges of this row are remarkably short, the length 

 decreasing from within outwards ; and in XiphorhynchiLS this 

 abbreviation has been carried to excess, all the plialanges of this 

 row being subequal and extremely short, while in both genera 

 they lie closely pi-essed together. In Dendrocolaptes these 

 phalanges are also short and subequal. 



ix. Summary. 



Miiller (6) was the first to utilise the structural chaiacters of 

 the syrinx for systematic pvu'poses. He it was who coined the 

 term " Tracheophone Passeres " and brigaded together the forms 

 possessing this type of windpipe. But his arrangement of the 

 Passeres as a whole was unsatisfactory, inasmuch as he failed to 

 discriminate between what we now regai'd as Passeres and the 

 outlying forms which go to make up the " Coraciiformes." 



Huxley appears to have been the first to differentiate between 

 the Passeriform and Ooiaciiform types : while the further subdi- 

 vision of the Passeres seems to have been first placed on a satis- 

 factory footing by Sclater and Salvin (10). These authors adopted 

 Miiller's " Tracheophonese," but for the sub-division of the group 

 which they found necessary they employed such characters as 

 were afforded by the scutellation of the ta,rsus, the shape of the 

 tail, and so on. Garrod (6) improved on this, and it will probably 

 materially aid those who may i-ead this paper if Garrod's scheme 

 is iriven here. It is as follows : — 



